#define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>
#include<math.h>
int main() {
    char a;
    while ((a = getchar()) != EOF) {
        getchar();
        if ((a >= 'A' && a <= 'Z') || (a >= 'a' && a <= 'z'))
            printf("YES\n");
        else
            printf("NO\n");
        
    }
    return 0;
}